1. Field of Invention
This invention generally relates to systems and methods for representing three-dimensional documents.
2. Description of Related Art
Techniques for creating virtual books, magazines, journals, textbooks, photograph albums, or the like, that attempt to simulate the appearance and functions of actual physical books, magazines, journals, textbooks, photograph albums, or the like, are highly desirable to the readers and viewers of these documents. These virtual books can be displayed by electronic books, i.e. e-book systems, personal computers (PCs), personal digital assistants (PDAs), or the like.
Many e-book systems, PCs, PDAs, or the like display virtual books in a two-dimensional (“2D”) manner or a three-dimensional (“3D”) manner. For example, B. Harrison describes several 2D-based e-book devices in “E-Books and the Future of Reading”, IEEE Computer Graphics and Applications, Vol. 10, No. 3, pages 32-39. However, displaying virtual books in a 3D manner provides a more realistic appearance of an actual physical book.
Modern graphics systems make it possible to represent virtual books on a computer screen creating a 3D appearance of physical books. Such 3D virtual books have many potential uses, such as, for example, the representation of historical manuscripts, the representation in electronic bookstores of books for sale, electronic book publishing, the basis of new forms of medical textbooks and other enhanced book formats, new forms of laboratory journals, or photograph albums. Although displaying virtual books in a 3D manner provides a better representation of an actual physical book compared to a virtual book displayed in 2D, there are several important issues that need to be addressed.
These issues include: 1) how to represent a closed book with either the front cover or the back cover visible; 2) how to represent an opened book with two adjacent pages visible; and 3) how to represent turning the pages of the book forwards or backwards. Page turning is particularly important to give the readers and viewers the impression of reading or viewing an actual physical book. Since page turning is a dynamic animation that not only starts, but also finishes with the book in a static opened or closed position, how the static positions of the book are represented affects, to a large degree, how the book should be represented during the page turning animation, and vice versa.
There are various e-book systems displaying electronic documents in a 3D manner. For example, U.S. Pat. No. 6,340,980 describes a special user interface device mimicking an actual physical book. When connected to a computer, this device works like any other user interface device such as a mouse. A software product, known as the Flip Browser®, has been developed by eBook Systems Inc., and can be found at http://www.flipbrowser.com.
Additionally, U.S. patent application 20020035697 describes systems and methods for distributing and viewing electronic documents. A software product, known as the Zinio Reader®, has been developed by Zinio Systems Inc., and can be found at http://www.zinio.com. Another system, the Turning the Pages® system is based on a multimedia authoring product called Macromedia. The Turning the Pages® system is jointly developed by the British Library and Armadillo Systems, and can be found at http://www.bl.uk/whatson/exhibitions/lindisfarne/ttp.html. Although the above describe and/or display electronic documents in a 3D manner, the disclosures regarding the page turning feature for virtual books displayed in a three-dimensional manner are limited to little or no detail of how the page turning features are designed or implemented.
U.S. Pat. Nos. 5,847,709 and 5,838,326 describe yet another system, commercially known as the WebBooks® developed by Xerox Corporation, for displaying electronic documents in a three-dimensional manner. Although the page turning animation of the WebBook® appears very similar to the page turning of an actual physical book, there are several drawbacks.
For example, an opened virtual book only models the top faces of the book, not the back side. Therefore, in a virtual environment where the back side or bottom faces, such as, for example, the front and back covers, of an opened virtual book is visible to the virtual camera, the virtual book no longer resembles an actual physical book. Thus, transitioning between a closed book and an opened book requires changing between the closed book representation and the opened book representation.
Additionally, WebBooks® include a page ruffling technique that simulates the multiple concurrent turning of a set of pages of the WebBook®. The pages to be turned are represented by multiple turning pages blocks. However, although the page ruffling technique provides the capability to rapidly scan through a set of pages for information of interest, the ruffling technique requires that the textures of all of the pages being turned to be displayed. Therefore, in WebBook®, all of the page textures are pre-loaded and stored in the main memory. Pre-loading and storing all of the page textures in the main memory severely limits the scalability of the system restricting the number of pages allowed in a virtual book. Furthermore, it is difficult to determine, even approximately, the amount of pages being turned during the page ruffling. Thus, other three-dimensional books have provided other solutions to resolve some of these drawbacks.